The Human Population 1 Think of the earth as a living organism that is being attacked by billions of bacteria whose numbers double every forty years. Either the …bacteria dies, or both die. - Gore Vidal

Scientists Disagree on Earth’s Carrying Capacity Figure 7.1

Scientists Disagree on Earth’s Carrying Capacity The following graphs show theoretical models of food supply and population size.

4 Freeways of LA

White Boards What do you think is the human carrying capacity on earth? (be prepared to explain) 5

6 HUMAN DEMOGRAPHY Demographics – The study of human populations and population trends.  Includes statistics about people such as births (fertility), deaths, life expectancy, migration, gender, race, age structures, and economic status.  Human Population reached 7 billion in 2011

7 POPULATION GROWTH For most of human history, humans have not been very numerous compared to other species.  It took nearly 72,000 years to reach 1 billion.  150 years to reach 3 billion.  25 years to reach 4 billion.  20 years to reach 5 billion  12 years to reach 6 billion. - Human population tripled during the twentieth century..

World Population “Dots” Video This video represents the growth of the human population since 0 A.D.video 8

9 Human Population History

The Calculations Given those conditions, estimated population size is:  N = Estimate of total population size  M = Total number of animals captured and marked on the first visit  C = Total number of animals captured on the second visit  R = Number of animals captured on the first visit that were then recaptured on the second visit N = MC / R

Changes in Population Size Crude birth rate (CBR)= the number of births per 1,000 individuals per year. Crude death rate (CDR)= the number of deaths per 1,000 individuals per year. - Global population growth rate = - (CBR- CDR)/ 10 - National population growth rate = - (CBR+ immigration) - (CDR + emigration)/ 10 - Doubling time (in years)- 70/growth rate

12 Human Population Growth Exponential Growth  Human population has increased  Rates of growth have also increased - Currently about 2% per year Doubling Time:  Estimation of how long for a population to double in size  When growth is exponential: - Doubling Time = 70 / annual % growth  70/2.0% = 35 years

Shanghai living 13

Different types of Growth Exponential growth is when the population and growth rate both increase. Linear growth is when only the population rate increases. The growth rate is steady. 14

White Boards Riddle: A wealthy, eccentric relative of yours passes away. You are listed as the primary beneficiary on the will. You have two options for collecting the money.  Option 1:$200,000 per day for thirty days.  Option 2: One penny doubled every day for thirty days 15

Solution Option 1: 30days x $200,000 = $6,000,000 Option 2:  Over $18,000,000! 16

24 hours of ships 17

Population Growth Populations show two types of growth  Exponential - J-shaped curve - Unlimited Growth - Growth is independent of population density  Logistic - S-shaped curve - Growth affected by environmental stress - Growth is not independent of population density

Exponential and Logistic Population Growth: J-Curves and S-Curves Populations grow rapidly with ample resources, but as resources become limited, its growth rate slows and levels off. Figure 8- 4

Exponential Growth N = N o e rt where  N o is the initial population size  r is the rate of growth in decimal form  t is the time (same units as the rate of growth) If the growth rate of an elephant population is 2%, starting with one male and one female, how many elephants would you have in 250 years?  297 elephants!

24 hour of airline traffic in US 21

Rule of 70 To determine the doubling time of a population, divide 70 by the percentage of growth.  Uses the exponential growth calculation  If the growth rate is 2%, then,  70 ÷ 2 = 35 years

Carrying Capacity (K) Exponential curve is not realistic due to carrying capacity of area Carrying capacity is maximum number of individuals a habitat can support over a given period of time due to environmental resistance (sustainability)

24 Two Demographic Worlds Developing countries are poor, young, and rapidly growing.  India, China, Bolivia (S. America), Congo (Africa)  Contain 80% of world population, and will account for 90% of projected growth. Developed countries are wealthy, old, and mostly shrinking.  United States, Japan, France  Populations often expected to decline.

New York City 25

26 Estimated Human Population Growth

27 Measurements of Population Growth Fertility Rate - Number of births per 1000 women per year.  Developing countries = ~20  Developed countries = ~10 Total Fertility Rate – Average number of children a woman has in her lifetime.  Congo = 4.41 India = 2.68 U.S. = 2.1 The replacement level is the total fertility rate required to offset the average number of deaths in a population for the current population to remain stable. 2.1 children per couple.

White Boards Is it ethical to tell people how many children they can have? 28

Fertility Rate of United States 29

30 Migration The movement of individuals between areas.  Emigration: Move out of an area  Immigration: Move into an area

Changes in Population Size Net migration rate- the difference between immigration and emigration in a give year per 1,000 people in the country.

32 Survivorship Life Expectancy - Average age a newborn can expect to attain in any given society.  Most affected by infant mortality rates.  Strongly correlated with income up to about $4, (U.S.) per person.

White Boards What happens if the number of retirees exceeds the number of working adults? What are we going to do about this in this in the United States? 33

Life Expectancy Infant mortality rate- the number of deaths of children under 1 year of age per 1,000 live births. Child mortality rate- the number of deaths of children under age 5 per 1,000 live births.

35 Life Expectancy

36 Population Growth : Opposing Factors Pronatalist Forces  Factors that increase the desire for children. - Source of pleasure, pride, comfort. - Source of support for elderly parents. - Current source of family income. - Social Status  Boys frequently valued more than girls.

37 Most antinatalist forces involve women. Women are less likely to have children when they have…  Higher education and personal freedom.  More opportunities to earn a salary.  Higher socioeconomic status Population Growth : Opposing Factors

38 United States Birth Rate

The Demographic Transition The theory of the demographic transition is the theory that as a country moves from a subsistence economy to industrialization and increased affluence, it undergoes a predictable shift in population growth.

40 DEMOGRAPHIC TRANSITION Model of how economic development alters population dynamics. 1. Preindustrial-slow population growth - Food shortages, malnutrition, lack of sanitation and medicine keep death rates high. - Birth rates tend to match death rates to maintain the population. 2. Early Transitional- rapid population growth - Hygiene, nutrition, and education improve. - Death rates drop dramatically. - Birth rates remain high initially. - Population increases very quickly.

41 DEMOGRAPHIC TRANSITION CONT’D 3. Late Transitional-stable population growth  Birth rates begin to fall.  Population may have increased from 2x to 4x by this point. 4. Industrial-declining population growth  Transition is complete.  Both death and birth rates are low.  Population is in equilibrium.

The demographic transition’s four stages Population growth is seen as a temporary phenomenon

43 Demographic Transition

White Boards What are other influences that could alter the path a country is on? 44

45 Age Structure (Population Pyramids) Distribution of ages in a population at a specific time. Visual representations of age structure within a country for males and females. Graphed as a population pyramid.  More young people in a population usually means higher growth rates.

White Boards What do you think the US pyramid would look like? 47

48 Age Structure Diagrams

49 FUTURE OF HUMAN POPULATIONS Most demographers believe the world population will stabilize sometime during the next century. We don’t know what the carrying capacity is?  Projections of maximum population size: - Low 8billion - Medium 9.3 billion - High 13 billion

The 12 Most Populous Countries in the World

Family Planning Family planning- the regulation of the number or spacing of offspring through the use of birth control.

The relationship between economic development and population growth rate for developing nations.

Ecological Footprints Affluence - having a lot of wealth such as money, goods, or property.

The IPAT Equation To estimate the impact of human lifestyles on Earth we can use the IPAT equation: I mpact= P opulation × A ffluence × T echnology

White Boards What do you think is the largest city on earth right now? (metro area) 56

The Impact of Affluence Gross domestic product (GDP)- the value of all products and services produced in a year in that country. GDP is made up of consumer spending, investments, government spending, and exports minus imports. A countries GDP often correlates with its pollution levels.

What will our future look like? New York City Billings, Montana

White Boards Do you have any questions? 60